Time

[LewisWildermuth]

In string theory or "M" theory, time is the fourth dimension of ten or eleven.

So we live in 4 (or 3 1/3 if you want to break up past present and future) dimensions.

Since there is not even a mathematical model on travel to the past (there are working models on travel into the future tho...), your scenario falls more into science fiction than science itself. But that has not stopped scientists from wondering about it.

Last I heard these are two of the possibilities of your scenario...

1. The second you shot your grandfather another universe, exactly like our own up until that point would be created and you would be trapped in that universe, in your original universe, the action would have never of happened, but you now would live in another universe where a man who would have been your dopplegangers grandfather was dead.

2. No matter how hard you tried, something would always prevent you from killing your grandfather and you would never succeed, thus preserving the time line.

There may be many more, but these are the ones I remember from my talks...

 

[fungle]

And if time is instantaneous there is no past or future
Time machines are redundant

 

[Phred]

You know... if travel to the past is possible then all the trips have already been made.

 

[Bushido216]

That's what I was thinking, which to me seems to make a paradox unlikely, since I remember asking this question yesterday.

Of course, those are just memories, did they really happen?

Anyway,

Volos, so, if you go to a parallel universe, isn't there some "super universe" if you will that oversights all of these universes? And what about the proposition that one could return to the past simply by travelling faster than light?